Guest essay by Sheldon Walker
It can be difficult to accurately estimate the warming rates of a temperature series, from a graph of temperature versus time. A global warming contour map makes this task easy, by colour coding all of the trends in the temperature series.
Global warming contour maps will be displayed for each of the 6 temperature series used in “Assessing recent warming using instrumentally homogeneous sea surface temperature records” by Zeke Hausfather, Kevin Cowtan, David C. Clarke, Peter Jacobs, Mark Richardson, and Robert Rohde.
The 6 temperature series are:
- Satellite radiometer record from 1997
- Buoy only record from 1997
- COBE-SST (Japanese record) from 1997
- HadSST3 from 1997
- ERSSTv3b from 1997
- ERSSTv4 from 1997
A detailed analysis of the contour maps will not be done in this article. The idea is for people to do their own analysis by looking at the contour maps. Some general comments will be made to assist people in understanding how a global warming contour map works. For example, how to work out if a temperature series has had a recent slowdown or pause.
First, the legend for global warming contour maps is displayed. This is used to convert a colour into a warming rate range, or a warming rate range into a colour. The same legend is used for all global warming contour maps.
Now the global warming contour maps for each of the 6 temperature series:
1) Satellite radiometer record from 1997
2) Buoy only record from 1997
3) COBE-SST (Japanese record) from 1997
4) HadSST3 from 1997
5) ERSSTv3b from 1997
6) ERSSTv4 from 1997
The first thing that should be noticed when looking at the 6 contour maps, is how similar they all are. Given that all of the temperature series are attempting to measure the same thing, it is reasonable to expect some similarity. But the contour maps are so similar, that you need to look closely to tell them apart.
It is worth comparing ERSSTv3b carefully with ERSSTv4. This will show you what effect “Karlization” has had on the ERSST temperature series (also used by GISTEMP).
If I had to separate these 6 contour maps based on whatever differences that there are between them, then I would group:
- the ERSSTv4 series,
- the Buoy only series, and
- the Satellite radiometer series, (this one could be in either group)
in one group.
- the COBE-SST (Japanese record)
- the HadSST3 series, and
- the ERSSTv3b series
in the other group.
This grouping is based on the size of the mid-green (pause or cooling) area near the centre of each contour map. The first group has a smaller mid-green area, and the second group has a larger mid-green area.
A quick comment on slowdowns and pauses. Has the recent slowdown or pause been removed?
Let me just say that:
- the light-green colour represents a warming rate of 0.0 to +1.0 degC/century, and
- the mid-green colour represents a warming rate of -1.0 to 0.0 degC/century (this is either a full pause (warming rate = zero) or cooling (warming rate < zero)
Have a look at any of the global warming contour maps above.
If you can’t see any green, then I suggest that you get your colour vision checked.
“Assessing recent warming using instrumentally homogeneous sea surface temperature records” by Zeke Hausfather, Kevin Cowtan, David C. Clarke, Peter Jacobs, Mark Richardson, and Robert Rohde. Science Advances 04 Jan 2017: Vol. 3, no. 1, e1601207 DOI: 10.1126/sciadv.1601207
The datasets: data available here in a ZIP file (17KB)